Interestingly enough, for what it's worth, with my first RRS (2008 / 2.7 TDV6 ) I asked the dealer here (in Adelaide, SA) when in for a srevice to do a 5 way rotation of my wheels, as the spare had never been used and the other 4 had been on the car since new. I cannot remember the kilometres travelled, but there was still ample tread left on the road tyres. All wheels were matching.

When I went to pick up the car they said they wouldn't do the rotation to include the spare as the difference in diameter between that and the other tyres was too great and it would cause the gearbox some grief. They went on to relate some horror stories customers have had by running odd size or uneven tyres on vehicles. Now I was somewhat horrified at that! My next set of tyres were bought as a set of 5, and I embarked on a 5,000km 5 way rotation policy.

When I bought my current RRS (2013 SDV6, fitted with the steel rimmed spare) I immediately purchased another wheel to match the road wheels and still rotate my tyres every 5,000 kms. The steel wheel is kept as an emergency only.

Hi Do you think this could be the problem I am having at the moment with my RRS Ive just had 4 new tyres on at main dealers now a week later Im getting a transmision fault flash up saying Ive lost some gears,
no first gear now and really hard work to pull away

The tyres were replaced with exactly the same make tyres that come off. I checked they were all the same and they were. the night we were travelling home when the transmission warning flashed up we managed to get back to our place, in the morning I was worried how I would get through town to the garage but started up and it must have righted itself because its been perfect since.
my ignition light which stayed on longer than it should was a alternater problem which they renwed on warrenty.
so hopefully alls ok now